new to muscle building.

Im 16 years of age, im 5 foot 9, 90kg, and I have quite a big build, im planning to all bulk it on muscle, but because im new I thought I should start with the triceps at home before I go to the gym properly, at the moment I have 2 5kg dumbells, can anyone guide me a little? do I need a timetable on what to eat throughout the week?